Sleep Training is Damaging

by | Jul 13, 2019 | Uncategorized


In this blog post I want to address one of the biggest concerns raised about sleep training, that it causes long-term damage to infants. As this fear is a big one, and as it’s rooted in science, this post is going to be a bit of a beast. So grab yourself a cuppa, or better yet, a cuppa and a bar of chocolate, and prepare to delve into the complex world of the stress response.


When we become stressed, something called the HPA axis is activated (babies, not surprisingly, are born with a very responsive HPA axis). One of the reactions of an activated HPA axis is the production of a hormone called cortisol, and it’s this hormone that is measured when we study babies’ stress levels (it’s a non-invasive procedure measured by saliva, so the tests themselves aren’t stressful). Cortisol is one of the hormones released in a fight-or-flight response. It plays a role in mobilizing our energy by temporarily suppressing things like our immune system, which we can manage without in the short term. You can see how this would be helpful if we were being chased or threatened. The problems with cortisol come when we produce too much of it in the long-term, and it’s this concern that’s raised by people who are against sleep training.


A while back, the American Academy of Pediatrics released a report entitled ‘The Lifelong Effects of Early Childhood Adversity and Toxic Stress’.  As the title suggests, this was focused on the adverse effects of long-term stress in children. But it also defined three types of stress that are helpful in how we think about it.


The first, a positive stress response, is the kind of stress that comes from-for example- getting a vaccination, going to nursery or being in a strange place. Provided there is support from a secure adult, this type of stress is actually quite good for children as it builds resilience and trust. The second, a tolerable stress response, is a slightly more extreme version of the first; a child suffering a bereavement or experiencing a natural disaster would be an example.  Again, these are made bearable by the support and security of an adult figure.


The third, on the other hand, is the focus of the study in question. This is the toxic stress that comes from a strong or long-term activation of the stress response. The causes tend to be factors such as child abuse, neglect or parental depression. This kind of stress can have a long-lasting effect on a child and lead to later issues such as chronic illness, substance abuse and an inability to form secure relationships.


I don’t think anyone would argue that sleep training falls into the second or latter category. If anything, it would fall into the first category as it’s done under the eye of a loving parental figure. Nonetheless, studies have shown elevated cortisol levels in babies left to cry it out, so it’s an understandable concern.





Let me clarify that ‘cry it out’ is only one sleep training method. It is called extinction; when you leave your baby in their room and do not go into until 7am and for any set timed feeds. More gentle sleep training methods are equally effective. However the idea that ‘’letting your baby cry is detrimental to their health’’ does need more investigation.


But how much cortisol are we actually talking about? To start with, we all have a small amount of cortisol present in our bodies naturally, being highest in the morning and lowest at around midnight. It’s not, therefore, a chemical that just appears in times of stress. It has natural fluctuations, regardless of what’s going on. There has been one well-documented study of mothers and babies who went to a residential facility to participate in a three-day extinction sleep training (a rather ominous word for cry it out with no reassurances). In fact, the study showed that there wasn’t much fluctuation in cortisol before and after the babies’ bedtime. It’s important to note that the babies already had elevated basal cortisol levels in the first place, presumably because they were in a strange environment. But it’s definitely interesting that their cortisol only went up a small amount, and on the second day not at all.


There haven’t been any reliable studies of stress on babies crying it out in their own homes, but we could reasonably expect that if there wasn’t a big fluctuation in cortisol in a strange environment- even with the variables- the fluctuations at home wouldn’t be vast. There have, however, been studies of stress on infants going to nursery. As you might expect, this does indeed cause elevated cortisol, particularly in the 2-3 year old age bracket, although in small amounts. However, most people still opt for daycare at some point before their children start school, basing their decision on practicality and the social needs of the child rather than on how detrimental it might be to their mental health. Gentler sleep training methods are done in a supportive way with regular checks or in room methods; all of which I use, so your baby knows you are right there. With nursery and childcare the settling in period is usually 2 hours to start with and then half a day, one day and so on. You will leave your baby longer without you when you settle at nursery then you will when you sleep train.


Given that minor amounts of stress are as inevitable for our little ones as they are for the rest of us, perhaps it’s better to think of sleep training as we do about nursery, weighing up the pros and cons rather than dismissing it as callous or harmful. Yes, there is a small amount of stress involved, but consider the following:


  • With a complete sleep plan; age appropriate routine, correct awake times, feeding amounts, bedtime environment and correct number of night feeds according to your baby there will be minimal tears if any.
  • Babies that sleep well have lower basal cortisol levels. In other words, they’re naturally more calm to start with
  • Sleep deprived mums and dads are far more likely to experience depression, which leads to increased stress levels in young children and adolescents
  • When a 3-6 month old baby plays with a sensitive and calm mother, their cortisol level decreases, but when a baby of the same age plays with an anxious mother, their cortisol either stays the same or slightly increases.


Another important point to note is that often when babies cry, their cortisol levels don’t change. This is because babies cry to communicate so many things, not just stress, and may even relieve tension by crying.


As the AAP report pointed out, not all stress is bad. Some stress is actually quite good, hence our bodies naturally equipping us with cortisol to deal with a little here and there. So whilst concerns about stress in sleep training are valid, it’s far better viewed in the wider context. A well-rested parent will have a happier relationship with their child, and vice versa. Young children who sleep well do much better in school and are far more able to handle minor upsets. Sleep training doesn’t damage a child as long as it’s practiced in a loving, safe environment. And if you weren’t a loving parent, you wouldn’t be investing in it in the first place!


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